McKennan was born in New Castle, Delaware on March 31, 1794, the son of Col. William and Elizabeth Thompson McKennan. He later moved with his family to Washington, Pennsylvania. He graduated from Washington College in 1810 and was admitted to the bar in 1814, commencing practice in Washington.
He worked as a tutor at Washington College in 1813, as he was studying law.[2] Later, he was a Trustee of the College and was often asked to be President of Washington College, but he refused every time.[2]
Despite immense pressure from associates, friends, and the Washington County Whig Party, McKennan again refused to run for another term in Congress, declaring that he had done his duty by serving in public office, and it was time to return to Washington, Pennsylvania, and focus on his law practice. In 1844, his supporters in his hometown of Washington, Pennsylvania, unsuccessfully tried to stir up interest in McKennan as a running mate for Henry Clay, and there is no indication that McKennan himself approved of the idea. McKennan also resisted efforts to entice him to run for governor of Pennsylvania in the 1840s, but in 1848, he served as president of the Pennsylvania electoral college.
Secretary of the Interior
Upon Millard Fillmore becoming the President of the United States, McKennan was offered the position of the United States Secretary of the Interior, but was reluctant to accept; only after intense pressure from friends and associates did he relent. Almost immediately, he regretted his decision, and resigned after a tenure of only 11 days. McKennan cited his "peculiar nervous temperament" which responded to excitement and depression for his reason to resign.[4] Contemporary accounts also cite disagreements with President Fillmore and Secretary of State Daniel Webster regarding the appointment and removal of attorneys, marshals, clerks, and heads of bureaus.[5] During his brief time as Secretary, McKennan was the head of the 1850 Census, which was being conducted that summer, and he issued a remarkably foresighted statement on the importance of protecting individual privacy:
Information has been received at this office that in some cases unnecessary exposure has been made by the assistant marshals with reference to the business and pursuits, and other facts relating to individuals, merely to gratify curiosity, or the facts applied to the private use or pecuniary advantage of the assistant, to the injury of others. Such a use of the returns was neither contemplated by the act itself nor justified by the intentions and designs of those who enacted the law. No individual employed under sanction of the Government to obtain these facts has a right to promulgate or expose them without authority.
...all marshals and assistants are expected to consider the facts intrusted to them as if obtained exclusively for the use of the Government, and not to be used in any way to the gratification of curiosity, the exposure of any man's business or pursuits, or for the private emolument of the marshals or assistants, who, while employed in this service, act as the agents of the Government in the most confidential capacity.[6]
Later career
Following his resignation, McKennan took on a less stressful job as the president of the Hempfield Railroad, which was then under construction between Wheeling, Virginia, and Greensburg, Pennsylvania, through his own town of Washington (in 1871, the Baltimore and Ohio Railroad purchased the financially hobbled Hempfield).
Personal life
On December 6, 1815, McKennan married Matilda Lourie Bowman. They had eight children together:
William McKennan
Thomas McKennan
Isabella McKennan
Jacob Bowman McKennan
Thomas McKean Thompson McKennan, Jr.
Anne Elizabeth McKennan
John Thompson McKennan
Matilda Bowman McKennan
McKennan died on July 9, 1852, in Reading, Pennsylvania, while on Hempfield Railroad business, and was interred at the Washington Cemetery in his long-time home of Washington, Pennsylvania.
